Uncomplicated urinary tract infections (UTIs) are common, with 40 to 50 percent of women reporting at least one UTI in their lifetime. Uncomplicated UTIs usually occur in a tract that is functionally and structurally normal. Complicated urinary tract infections are those that occur in men, elderly persons, pregnant women, and patients with an indwelling catheter or an anatomic or functional tract abnormality. Jancel and Dudas review the prevention and treatment of uncomplicated cystitis.
Uncomplicated infections are generally benign but, if not treated, can interfere with daily life. In healthy women, long-term adverse effects are rare. As many as 80 percent of infections are caused by Escherichia coli, and Staphylococcus saprophyticus accounts for another 5 to 15 percent. A small number of infections are caused by Enterococci, Klebsiella species and Proteus mirabilis. Antibiotics that are most useful to treat uncomplicated cystitis are well-tolerated, cover expected uropathogens, and have favorable pharmacokinetic profiles. The best tolerated cures use antibiotics, such as trimethoprim-sulfamethoxazole (TMP-SMX) or fluoroquinolones, that have little effect on vaginal and fecal bacterial flora.
It is important for physicians to know local resistance patterns because most uncomplicated UTIs are treated empirically. Resistance to TMP-SMX, ampicillin, and first-generation cephalosporins has been increasing in some communities. In 1998, resistance to E. coli was twice as common in the western United States than in the Northeast. Empiric therapy is probably useful only in communities where resistance rates are less than 10 to 20 percent.
Besides resistance patterns, antibiotic choice should include consideration of the patient's allergy history, the cost and tolerability of the medication, and previous antibiotic use. TMP-SMX has been the standard therapy for UTIs; patients with a sulfa allergy can take trimethoprim alone and achieve a similar cure rate. Side effects include skin rash, nausea, and vomiting. Patients who are concomitantly taking sulfonylureas need glucose monitoring because of the enhanced glucose-lowering effects of TMP-SMX. TMP-SMX therapy should be avoided in patients with liver impairment.
Fluoroquinolones (e.g., ciprofloxacin and levofloxacin) provide good coverage for common uropathogens and cause minimal side effects. Fluoroquinolones should not be taken with products that contain cations, because absorption of the fluoroquinolones will be decreased. Women who are pregnant or breast-feeding should also avoid these antibiotics.
Beta-lactam antibiotics are no longer useful as first-line treatment for UTIs because of increased resistance and higher recurrence rates compared with other agents; however, they may be useful if urine culture indicates susceptibility. Third-generation cephalosporins (e.g., cefixime and cefpodoxime) have lower resistance rates and longer half-lives, allowing for less frequent dosing. The most common side effects of the beta-lactams include rash, nausea, abdominal pain, vomiting, and headache.
Nitrofurantoin can be used in patients with normal renal function. Side effects are rare but may include malaise, cough, and dyspnea. Pulmonary fibrosis may rarely occur with long-term use. Fosfomycin is used as a single-dose treatment that is generally well tolerated but may cause diarrhea, nausea, vomiting, or esophageal discomfort. Antibiotics and dosing information for the treatment of UTIs are listed in (see accompanying table).
Although single-dose therapy using betalactams, TMP-SMX, trimethoprim, and fluoroquinolones has a high cure rate, single-dose therapy is associated with a high rate of recurrence within six weeks of initial treatment. Reinfection may come from organisms remaining in the perianal area. Multiple-day regimens are considered more effective, although single-dose regimens are easier to use and generally better tolerated. Short-course therapy using three days of antibiotics appears to provide similar eradication rates with fewer side effects than a seven- to 10-day course. Patients who may benefit from the longer course of therapy include women who are pregnant, who have diabetes mellitus, or who have a history of urinary tract symptoms.
Patients with recurrent UTIs can be offered continuous low-dose antibiotic prophylaxis, patient-initiated treatment, or postcoital prophylaxis taken within two hours of sexual intercourse, if infection is associated with sexual activity. Urine culture is appropriate before prophylactic therapy is started to establish the susceptibility of the pathogen. Patient-initiated therapy using a short course of antibiotics may be successful in younger women.
The authors conclude that TMP-SMX and the fluoroquinolones (when TMP-SMX resistance is greater than 10 to 20 percent) are useful first-line treatments for uncomplicated cystitis. Other options include a seven-day course of nitrofurantoin or a single dose of fosfomycin.